Neuropeptide Y (“NPY”), a 36 amino acid peptide neurotransmitter, is a member of the pancreatic family of peptides and shares significant sequence homology with pancreatic polypeptide and peptide YY. Human neuropeptide Y (“hNPY”) has the sequence: H-Tyr-Pro-Ser-Lys-Pro-Asp-Asn-Pro-Gly-Glu-Asp-Ala-Pro-Ala-Glu-Asp-Met-Ala-Arg-Tyr-Tyr-Ser-Ala-Leu-Arg-His-Tyr-Ile-Asn-Leu-Ile-Thr-Arg-Gln-Arg-Tyr-NH2 (SEQ ID NO:1). NPY was discovered, isolated and sequenced from porcine brain and was named “neuropeptide Y” due to its isolation from neural tissue and the presence of tyrosine as both the amino and carboxy terminal amino acid.
NPY and the other members of its family of peptides all feature a tertiary structure consisting of an N-terminal polyproline helix and an amphiphilic α-helix, connected with a β-turn, creating a hairpin-like loop, which is sometimes referred to as the “pancreatic polypeptide fold.” The helices are kept together by hydrophobic interactions. The amidated C-terminal end projects away from the hairpin loop.
Subsequent to its discovery, NPY was identified as being the most abundant peptide in the central nervous system with widespread distribution including the cortex, brainstem, hippocampus, hypothalamus, amygdala, and thalamus, as well as being present in the peripheral nervous system in sympathetic neurons and adrenal chromaffin cells.
NPY seems to fulfill the main neurotransmitter criteria, since it is stored in synaptic granules, is released upon electrical nerve stimulation, and acts at specific receptors. It is clear that NPY is an important messenger in its own right, probably in the brain, where NPY potently inhibits the activity of adenylate cyclase and induces an increase in the intracellular levels of calcium. Central injection of NPY results in blood pressure changes, increased feeding, increased fat storage, elevated blood sugar and insulin, decreased locomotor activity, reduced body temperature, and catalepsy.
NPY appears to interact with a family of closely related receptors. These receptors are generally classified into several subtypes based upon the ability of different tissues and receptors to bind different fragments of neuropeptide Y and the closely related PYY. The Y1 receptor subtype (“NPY-Y1 receptor”) appears to be the major vascular NPY receptor. The Y2 receptor subtype (“NPY-Y2 receptor”) can also occur postjunctionally on vascular smooth muscle. The Y3 receptor subtype (“NPY-Y3 receptor”) appears to be NPY-specific, not binding PYY. This receptor is likely to be present in the adrenal tissues, medulla, heart, and brain stem, among other areas. For a review of neuropeptide Y and neuropeptide Y receptors, see, e.g., C. Wahlestedt and D. Reis, Annual Review of Pharmacology and Toxicology, 33:309-352 (1993). Patent Cooperation Treaty (“PCT”) Publication No. WO 95/00161 describes a series of NPY antagonists and agonists for controlling biological activities such as obesity and cardiovascular function.
European Pat. No. 0759441 and U.S. Pat. No. 5,576,337 report that physiological disorders related to an excess of neuropeptide Y include: disorders or diseases pertaining to the heart, blood vessels or the renal system, such as vasospasm, heart failure, shock, cardiac hypertrophy, increased blood pressure, angina, myocardial infarction, sudden cardiac death, arrhythmia, peripheral vascular disease, and abnormal renal conditions such as impaired flow of fluid, abnormal mass transport, or renal failure; conditions related to increased sympathetic nerve activity for example, during or after coronary artery surgery, and operations and surgery in the gastrointestinal tract; cerebral diseases and diseases related to the central nervous system, such as cerebral infarction, neurodegeneration, epilepsy, stroke, and conditions related to stroke, cerebral vasospasm and hemorrhage, depression, anxiety, schizophrenia, and dementia; conditions related to pain or nociception; diseases related to abnormal gastrointestinal motility and secretion, such as different forms of ileus, urinary incontinence, and Crohn's disease; abnormal drink and food intake disorders, such as anorexia and metabolic disorders; diseases related to sexual dysfunction and reproductive disorders; conditions or disorders associated with inflammation; respiratory diseases, such as asthma and conditions related to asthma and bronchoconstriction; and diseases related to abnormal hormone release, such as leutinizing hormone, growth hormone, insulin, and prolactin.
PCT Publication No. WO 02/43776 by Reubi reports on the use of compounds that bind the NPY-Y1 receptor for the preparation of a pharmaceutical composition for the diagnosis or treatment of tumors expressing the NPY-Y1 receptor, in particular breast cancer, ovarian cancer and glioblastoma.
There are numerous patents and patent publications that disclose certain NPY analogues and uses thereof, such as U.S. Pat. Nos. 5,026,685, 5,328,899, 6,511,984, PCT Publication No. WO 02/43776, PCT Publication No. WO2007/039318, etc. Notwithstanding the foregoing, there remains a continuing need for NPY analogues having improved potency and/or selectivity and/or in vivo or in vitro characteristics.